Integral fin canister-nozzle exit cone



April 16, 1968 G 055 ET AL 3,378,216

INTEGRAL FIN CANISTER-NOZZLE EXIT CONE Filed April 29, 1966 GEORGE K 035DAN/V) D. DU/VFEE ROLAND C. WEBSTEI? BY gM AGE/V T INVENTORE UnitedStates Patent INTEGRAL FIN CANTlSTER-NOZZLE EXIT CONE George K. Oss,Springfield, Danny D. Dunfee, Fairfax County, and Roland C. Webster,Annandale, Va, as-

signors to The Susquehanna Corporation, a corporation of Delaware FiledApr. 29, 1966, Ser. No. 546,448 7 Claims. ('Cl. 244-334) ABSTRACT OF THEDISCLOSURE This invention relates to an integral fin and nozzleexpansion cone assembly for a rocket wherein the expansion nozzle isused as a support for the fin canister and both the nozzle expansioncone assembly and the fine canister are removable and changeable.

The ability of a rocket to maintain its predetermined trajectory isdependent, in large part, upon the aerodynamic design of the rocketcasing and the placement and efficiency of its stabilizing fins. Forexample, a factor greatly alfecting overall rocket performance is thedesign of the exit cone, for it is by this means that the expansion ofthe motive gases is con-trolled in great part. The expansion cone isgenerally designed for the atitude range at which the motor will do mostof its operating; for example, if the rocket is meant to be boosted tohigh altitude before main motor ignition one type of cone is preferable,while in the case of a rocket with low-altitude ignition it isadvantageous to use an expansion cone which is specifically designed forlow-altitude flight. In the past, and as evidenced by the prior art, thepractice was to design each rocket structurally and aerodynamicallyspecifically to match the qualifications and parameters required for aparticular task. This was acceptable in the days when rockets weremanufactured in small numbers in comparison with today, but with morewidespread use there came a demand for increased versatility and lowercosts per unit. It is now advantageous for the rocket manufacturer toproduce and stock a minimum number of standarized rocket motors,casings, and air-frames, and to rely upon changes in accessorycomponents in order to vary operating characteristics. For this reasonthere exists a demand to provide for a maximum interchangeability ofparts and accessories in order to enable this minimum number of shelfitems to perform the maximum number of tasks.

Considering the specific problems encountered in the design of fins andnozze expansion cone assemblies, and in line with the aforementioneddesires, the instant invention provides a new and simple means forproviding a basic rocket motor and air-frame design with a maximum ofversatility by providing an easily interchangeable fin and nozzleexpansion cone assembly. It is well-known in the art that installationof the stabilizing fins far back on the rocket vehicle adds to stabilityand that a reduction in aerodynamic drag is provided by a smooth contourthroughout the length of the rocket. In addition, as the distance fromfin to vehicle center of gravity is increased, the size of the fin canbe decreased and still provide the same degree of stabilization. By theteaching of the instant invention the stabilizing fins are mounted asfar aft as is possible on the rocket vehicle. The design also eliminatesa usual component by using the expansion nozzle as the rear fin support.By the construction of the instant invention, both the nozzle expansioncone and fin canister are removable and changeable, allowingsubstitution of t 3,378,216 Patented Apr. 16, 1968 to fins havingparticular aerodynamic characteristics. By combining, in an integrated,interchangeable structure, a set of stabiizing fins and -a nozzle conewhich have been matched to a particular set of parameters, the instantinvention provides a means by which a basic rocket motor and air-framemay be quickly and easily tailored to a specific task.

It is the primary object of the intsant invention to provide an improvedintegral fin and nozzle expansion cone assembly for rockets.

Another object of the invention is to provide a improved fin assemblywhich contributes to the aerodynamic stability and reduces the drag ofthe rocket vehicle.

Still another object of the invention is to provide an integral fincanister and nozzle expansion cone assembly in which the expansion coneis removable and interchangeable.

An additional object of the present invention is to provide a finassembly in which the size and weight of the fins and the mountingelements are kept to a minimum.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description Whenconsidered in conjunction with the accompanying drawing wherein:

FIGURE 1 is a perspective view showing the integral fin and expansioncone assembly of the invention in position for mounting on the rocketcasing;

FIGURE 2 is a side elevation, partially in cross-section, showing indetail the elements of the instant invention; and

FIGURE 3 is a side elevation, partially in cross section, of analternate embodiment of the expansion cone of the instant invention.

In FIGURE 1 there is shown the main body 10 of a rocket including theair-frame and rocket motor, with the improved integral fin canister andnozzle expansion assembly 11 sohwn in position for attachment to themain body 10. Assembly 11 consists of a fin canister 12, fins 13, 14,15, and 16, and an expansion cone, which is not visable in the view.

In FIGURE 2 the elements of the inst-ant invention are shown in detail.A motor case 19 of any standard design has a terminal portion 20 whichcontains nozzle insert 21, also of design known in the art. It is to theterminal portion 29 of the rocket motor case that the integral fin andexpansion cone assembly 11 is attached. Forming the nucleus of assembly11 is a truncated cone-shaped adapter element 22, the design of which iscomplementary in shape to the terminal portion 20 of the motor case.This adapter element 22 is provided with a threaded portion 24 at theend having a minimum radius and with a plurality of holes along thesides through which screws 23 are passed in order to mate the adapterelement to the motor case. Expansion cone 17 is preselected to providethe proper degree of expansion and is provided at its forward end with athreaded portion 25 by means of which it will screw into adapter element22. Expansion cone 17 is also provided at its forward end with a sealingmeans such as an O-ring seal 26, which will preclude the escape ofpropulsion gases between it and the end of nozzle 21, but this O-ringseal '26 could also be installed in the rear portion of adapter element22.

As aforestated, it is desirable to mount the stabilizing fins as farrearward as is possible, for this contributes to the aerodynamicstability of the vehicle and also, since the fins are a greater distancefrom the vehicles center of gravity, it allows for the use of smallerfins to maintain the same stabilization influence, thus saving weightand expense. Pins 13, 14, 15, and 16 are most desirably mounted byfixedly attaching them to a fin canister 12 by any conventional meanssuch as a plurality of welds 18. In order to preserve the streamlinedshape of the rocket vehicle, fin canister 12 is preferably of the sameoutside diameter as motor casing 19, and thus no undesirable floweffects are created in the area of the fins. In the preferred embodimentthe largest diameter of the expansion cone is equal to the insidediameter of the fin canister, so that the streamlining of the vehiclemay be maintained, although larger expansion cones may be used. The useof a large cone having an end diameter greater than that of fin canister12 results in a portion 30 of the cone breaking the aerodynamiccontinuity of the vehicle at a sacrifice in desirable flightcharacteristics. However, if the vehicle is boosted to operatingaltitude, these undesirable characteristics are minimized. If it isdesired to use an expansion cone which allows less expansion of gases,that is, one which has a smaller exhaust diameter such as is used at lowaltitudes, to be in keeping with the present invention such a cone isequipped with an outside flange 29 which increases its final outsidediameter to that of fin canister 12. Such a construction is shown inFIGURE 3. The reason for this will be explained hereinafter when themethod of assembly of the various components is discussed. Fin canister12 is equipped in its forward portion with a plurality of screws 27which are adapted to fit into cooperating holes in adapter element 22 inorder to attach the fin canister thereto. As for the rear mounting ofthe fin canister, it is accomplished by means of a plurality of setscrews 28 which are tightened down to engage flange 29 on the expansioncone 17.

The elements of the instant invention may be assembled as a unit andthen installed on the rocket case or they may be placed piece by pieceon the vehicle. The first step of unit assembly consists or attachingtogether adapter element 22 and the preselected expansion cone 17 bymeans of their screw threads 24, 25 respectively. Then the fin andcanister assembly is slid over the adapter plate and expansion cone suchthat screws 27 may properly engage adapter element 22 and the forwardend of the fin canister is thereby fastened. This will place set screws28 on the rear portion of fin canister 12 in alignment with flange 29 ofthe expansion cone 17, and the tightening of these screws provides rearsupport for the fin canister while also locking expansion cone 17against rotation on threads 24-. The final step in this mode is toinstall the integral assembly on the rocket air-frame 10 by slipping itover the nozzle cone on the terminal portion 20 of the motor casing 19and then attaching it by means of screws 23 to threaded holes in therocket casing.

In a second method of assembly the adapter portion 22 is first placedabout terminal portion 19 of the motor casing and attached thereto, andthe expansion cone is then screwed on. In the final step the fincanister assembly is slipped over both adapter and cone and fastened byscrews 27 and set screws 28. The importance of flange 29 on theexpansion cone 17 is now seen, for it is by means of this flange thatrigidity is given to the entire assembly; the rear of the fin canisteris supported and the expansion cone 17 is locked against rotation. Forthis reason it is preferred that each expansion cone used in theinvention, no matter what the exhaust opening diameter, be extended bymeans of a flange such that the final outside diameter is substantiallyequal to the inside diameter of fin canister 12, thus allowing thelocking action by set screws 28. The elements of the integral fincanister expansion cone assembly may be preassembled and shippedseparate of the rocket air-frame 10 to be assembled some time prior tolaunch as a unit, or these elements may be installed one by one onto therocket. Once the unit has been installed on the rocket vehicle it isstill possible to effect a change of expansion cone by simply looseningset screws 28, unscrewing the expansion cone from the adapter plate, andreplacing it with a new one. Thus, the user is able to make last-minutechanges in the field, if necessary. The same sort of last-minuteiutertlhangeability also applies to the fins and fin n swr.

It is thus seen that the instant invention provides a simple, efiicient,and reliable means for attaching any one of the preselected designs ofnozzle expansion cones and stabilizing fins in order to best match thedesired vehicle flight characteristics, operating parameters, andoperating altitude. In addition to providing means for quick fieldchange of expansion nozzle and fin components when it is desired at thelast minute to change the operating altitude or flight characteristicsof the rocket vehicle; the concept of the instant invention facilitateseasy packing and shipping of rocket motor casings and associatedcomponents since the expansion cones and fins can be shipped separatelyand easily installed immediately prior to use.

The number of designs of nozzle expansion cones and fins that can beadapted for use with the instant inventive concept is great, and it isnot the intention to restrict them to the designs shown in the drawing.Obviously, many modifications and variations of the present inventionare possible in the light of the above teachings. It is, therefore, tobe understood that within the scope of the appended claims the inventionmay be practiced otherwise than is specifically described.

What is claimcd as new and desired to be secured by Letters Patent ofthe United States is:

1. For a rocket vehicle having a motor, a motor case and a motor nozzle,an integral fin and nozzle expansion cone assembly comprising:

a fin canister having a forward portion and a rearward portion,

a plurality of fins mounted on the outside of said canister supportedentirely by said canister,

an adapter element,

means for removably attaching said forward portion of said fin canisterto said adapter element,

an expansion cone,

means for removably attaching said expansion cone to said adapterelement,

means for removably supporting said rear portion of said canister on therear portion of said expansion cone, and

means for removably attaching said adapter element to said motor caseadjacent to said nozzle such that said expansion cone is abutting saidnozzle and is in fluid communication therewith.

2. The structure of claim 1 wherein said means for attaching saidadapter element to said expansion cone comprises a threaded fitting.

3. The structure of claim 1 wherein said means for supporting said rearportion of said canister comprises:

a flange of outside shape and size substantially equal to the insideshape and size of said canister and attached to said expansion cone, and

locking means installed in the periphery of said canister and acting onsaid flange whereby said expansion cone is locked against movement.

4. The structure of claim 1 further including:

seal means interposed between said nozzle and expansion cone wherebyleakage of propulsion gases be tween said nozzle and said expansion coneis preeluded.

5. The structure of claim 4 wherein said motor case and said fincanister are of cylindrical shape and of equal outside diameter, andsaid adapter element and said expension cone are positioned within saidcanister.

6. The structure of claim 5 wherein said adapter element is a truncatedcone concentrically mounted about said nozzle.

7. For a rocket vehicle having a motor, a cylindrical motor case and apropulsion nozzle, an integral fin and nozzle expansion cone assemblycomprising:

a fin canister of cylindrical shape having an outside diameter equal tothe outside diameter of said motor case,

a plurality of outwardly oriented fins fixedly attached to saidcanister,

a plurality of inwardly acting set-screws installed about the rearperiphery of said canister,

an adapter element of truncated conical shape having a maximum outsidediameter equal to the outside diameter of said motor case,

an inwardly oriented threaded section on the rear portion of saidadapter element,

means for removably attaching said adapter element to said motor caseadjacent said nozzle,

means for removably attaching said fin canister to said adapter element,

a nozzle expansion cone,

an outwardly oriented threaded section on the forward portion of saidexpansion cone adapted to coact with said inwardly oriented threadedsection to removably attach said adapter element to said expansion cone,

a flange of diameter substantially equal to the inside References CitedUNITED STATES PATENTS 3/1957 Apotheloz et al 244-328 7/1963 Iasse2443.29

BENJAMIN A. BORCHELT, Primary Examiner. SAMUEL FEINBERG, Examiner.

V. R. PENDEGRASS, Assistant Examiner.

